Recently, owing to popularity of information terminals using video and audio recording functions, electronic mails using video or audio as well as text (video mail and audio mail, respectively) are increasing aside. Generally, in exchange of electronic mails, a receiver of an electronic mail often sends a reply mail by citing a part or whole of the received mail and/or newly adding a text. In video or audio mail, a system of replying by citing a part or whole of the received video or audio mail is proposed, for example, in patent document 1.    Patent document 1: JP2000-209347